The invention relates generally to an improved chemical vapor deposition (CVD) method for creating films on substrates. More particularly, the invention relates to an improved CVD method for creating films of diamond or similar material on substrates. Even more particularly, the invention relates to an improved CVD method for creating films on substrates whereby the substrate is not damaged. The enhanced CVD of the diamond or other material is accomplished by depositing seed particles onto a suitably charged surface prior to the CVD step.
Material properties in various applications can be improved by the application of film coatings having superior properties relative to the substrate material. Some of the better film materials are difficult to apply however, since creation of some of the most stable film surfaces require large amounts of energy. One technique for creating films of high surface energy materials such as carbides, nitrides, borides, oxides including lead, zirconate titanate, etc. is the known technique of chemical vapor deposition. One of the most desirable coatings is that of diamond, due to its superior properties related to high hardness, low coefficient of friction, high thermal conductivity, heat and corrosion resistance, etc. Applications in which diamond coatings are useful include wear surfaces such as cutting tools, heat sinks for electronic devices, microwave power devices, electro-optical devices, etc. However, application of diamond films, even via the CVD technique, is difficult because of the nature of the material itself.
Most CVD techniques currently employed to create diamond films on a substrate require the substrate surface to be damaged in some manner. For example, it is known to improve CVD of diamond by polishing or scratching the substrate surface, ultrasonicating the surface in a diamond suspension, or etching the surface with plasma. Obviously, damage to the surface of the substrate is not desirable in many applications, such as when the substrate is a silicon wafer to be used in microelectronics. Films created by these techniques are typically patchy and non-uniform with many areas of the substrate remaining uncovered. Valdes et al. has reported a non-damaging electrophoretic technique for depositing diamond in "Selected Area Nucleation and Patterning of Diamond Thin Films by Electrophoretic Seeding" (J. Electrochem. Soc., 138, 635-636 (1991). This technique utilizes an electric field to cause deposition from a colloidal suspension of diamond seeds onto a substrate, which is then treated via conventional CVD to grow a diamond film. This technique results in better coverage, but is limited in that it requires a conductive substrate.
The method of the invention is a non-damaging technique utilizing conventional CVD for growth of diamond films or the like on substrates of any composition, e.g., plastic, glass, metal or ceramic. The method results in rapid, uniform growth of a continuous film, with the ability to control grain size. The method is successful on substrates of any surface configuration, whether electrically conductive or non-conductive. Film growth is several times faster than under the known techniques.